fix: double delete events are handled correctly

[jamespfaulkner]

stream-registry PR

DefaultEntityViewUpdater to handle receiving double delete events correctly.

Details

The delete logic is slightly convoluted. Whenever we receive a delete event, we look up the original entity (if it exists) and keep a record of it so that agents are able to reconcile deletes using the last state of the entity prior to being deleted.

In some cases in the future, it might be required to "double send" deletes. E.g. a Delete event is sent for an entity that has already been deleted. Before this change, any subsequent delete event would cause the reference to the last state of the entity to be lost. Now it doesn't.

It's worth noting that in normal operations, when an agent is handling events on demand, this doesn't cause too many problems since the first delete event will be reconciled while the last known state of the entity is still available. However, this can cause problems for agents that are running scheduled reconciliation processes.

Changed

Now handles receiving the same delete event multiple times correctly.

PR Checklist Forms

• CHANGELOG.md updated
• Reviewer assigned
• PR assigned (presumably to submitter)
• Labels added (enhancement, bug, documentation)